Oxidative Stable Cu3Sn Nanoparticles for Novel Electrode Fabrication Using Pressure Under Ambient Condition

Manufacturing methods of conductive electrode is essential technology for printable electronics such as radio frequency identification tags (RFID), thin film transistor (TFT), ultra high frequency antennas and solar cell. Various fabrication methods of electrodes for printable electronics have been suggested to screen printing, gravure printing and inkjet printing. However, these methods have difficulties to the control of printing pressure, thickness, nozzle blocking, viscosity of ink and coffee ring effect. New technique for electrode for printable electronics needs to perform at room temperature and ambient condition.

In addition, copper nanoparticles are good prospective candidate to replace high cost silver because of low-cost, abundant deposit and high conductivity. However, copper nanoparticles have the limitation which is highly oxidative materials and these drawbacks limited practical printing process. To overcome these limitations, conductive materials for electrodes requires high oxidative stable nanoparticles and low cost materials. In this study, we synthesized high oxidative stable, conductive Cu₃Sn Nanoparticles and fabricated electrode by pressure assisted method at room temperature and ambient condition.

Prepared Cu₃Sn nanoparticles were confirmed using X-ray diffraction (XRD) and Energy Dispersive X-ray Spectrum (EDS) with High Angle Annular Dark-Field Scanning TEM (HAADF-STEM). Measurement of electrical conductivity was carried out with the 4-point probe methods depending on various value of pressure. The conductive electrodes were obtained by pressure at 530MPa and showed electrical resistivity of less than 19.8 µΩ cm. Electrical resistivity of fabricated electrodes is similar to that of bulk Cu₃Sn material (8.8. µΩ•cm). This result is caused by numerous and three dimensional contact of each conductive nanoparticle. To investigate the contact of each nanoparticle, Cross-sectional TEM analysis of pressed nanoparticles was performed. Also, we analyzed oxidation stability of nanoparticles by XRD and change of conductivity during 4 weeks in harsh condition (50% RH, at 25 ^oC). XRD and conductivity variation results showed no significant degradation. From these results, Cu₃Sn nanoparticles have highly stable against air oxidation.

In conclusion, we synthesized high oxidative stable, conductive Cu₃Sn Nanoparticles and fabricated electrode by pressure assisted method at room temperature and ambient condition. The Cu₃Sn nanoparticles were stable in air due to the low Gibbs free energy and have very low price. Pressure assisted method promotes the contact of each particle which induce low electrical resistivity at room temperature and ambient condition. We believe that Cu₃Sn nanoparticles and pressure assisted method for fabrication of electrode make a great contribution to TFTs, Solar Cell and RFID for electronics.